This Small Business Innovation Research Phase I project aims to develop new targeted fluorogenic substrates capable of measuring lysosomal enzyme activity in living cells and tissues. If successful, the proposed research will provide breakthroughs needed to advance the discovery of promising new therapies and modulating drugs for lysosomal storage diseases and allied medical applications. In Phase I of this project, Marker Gene Technologies, Inc. will establish the feasibility of the technology by preparing new fluorogenic glycosidase substrates for lysosomal enzymes and demonstrating differential staining in living cells that are from normal or are of disease origin. In Phase II, these new substrates will be assayed in vitro and in vivo for their ability to measure specific and localized inhibition or induction of lysosomal enzymes in living cells as well as differentiate individual enzyme activities in a cell- or tissue-specific manner. The new substrates and the resulting detection systems will provide innovative methods to quantitate lysosomal enzyme function and to screen for the influence of secondary drug or protein administration, making them useful analytical tools for a variety of significant medical applications. The success of this project opens up enormous commercial possibilities in the fields of medical intervention in lysosomal storage diseases such as Sandhoff's disease, Tay-Sachs syndrome, Krabb[unreadable]'s disease and Gaucher's disease, as well as in the screening of new proteins and drugs in cell-culture systems for efficacy in modulating lysosomal enzyme activity in these diseases, and development of new, general and specific high-throughput lysosomal enzyme detection strategies. In addition, it will lead to commercial and licensable products in these areas. [unreadable] [unreadable] [unreadable]